What is the appropriate number of maxEntries

[rayhym]

I understand that the maxEntries should be a power of two (as discussed in this old thread How is the parameter maxEntries interpreted by the Eviction Algorithms?)

However, when I set the maxEntries to 1024 and put a hash map with size 1000 into a cache. In the end, it holds only 959 elements.

Then, I tried to set the maxEntries to 1500. This number could hold all 1000 elements.

But I don't want to randomly estimate the maxEntries number.

Are there any formula or best practice to deal with maxEntries number?

Thank you in advance.

[william.burns]

In the current versions if the maxEntries is not a power of 2 we just find the next lowest one.  So in the case of setting it to 1500 the max entries would 2^11 = 2048.

Also maxEntries contract is just that you will not get above that, it doesn't guarantee that if you keep adding it will keep growing.  This is because we do this based on the segments available in the data container (controlled by the concurrency level) just like ConcurrentHashMap.  http://infinispan.org/docs/7.0.x/faqs/faqs.html#_cache_s_number_of_entries_never_reaches_configured_maxentries_why_is_th…  If you set the concurrency level to 1 then you would be able to get up to 1024 much easier, however you would have extremely high levels of contention as there is only 1 segments for all of the keys and you will run most likely run into locking issues with concurrent updates.